[07/15] dmaengine: dw: revisit data_width property
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Message ID 1453663322-14474-8-git-send-email-mans@mansr.com
State Changes Requested
Headers show

Commit Message

Mans Rullgard Jan. 24, 2016, 7:21 p.m. UTC
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

There are several changes are done here:

 - Convert the property to be in bytes

   Much more convenient than keeping encoded value.

 - Use one value for all AHB masters for now

   It seems in practice we have no controllers where masters have different
   data bus width, we still might return to distinct values when there is a use
   case.

 - Rename data_width to data-width in the device tree bindings.

 - While here, replace dwc_fast_ffs() by __ffs().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mans Rullgard <mans@mansr.com>
---
This patch changes the DT binding, so it should probably be amended for
compatibility with old device trees.  I've included it as is since I think
the change as such is good.
---
 Documentation/devicetree/bindings/dma/snps-dma.txt |  5 ++-
 arch/arc/boot/dts/abilis_tb10x.dtsi                |  2 +-
 arch/arm/boot/dts/spear13xx.dtsi                   |  4 +--
 drivers/dma/dw/core.c                              | 40 +++-------------------
 drivers/dma/dw/platform.c                          |  8 ++---
 drivers/dma/dw/regs.h                              |  2 +-
 include/linux/platform_data/dma-dw.h               |  5 ++-
 7 files changed, 16 insertions(+), 50 deletions(-)

Comments

Vineet Gupta Jan. 25, 2016, 7:32 a.m. UTC | #1
On Monday 25 January 2016 12:55 AM, Mans Rullgard wrote:
> From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>
> There are several changes are done here:
>
>  - Convert the property to be in bytes
>
>    Much more convenient than keeping encoded value.
>
>  - Use one value for all AHB masters for now
>
>    It seems in practice we have no controllers where masters have different
>    data bus width, we still might return to distinct values when there is a use
>    case.
>
>  - Rename data_width to data-width in the device tree bindings.
>
>  - While here, replace dwc_fast_ffs() by __ffs().
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Mans Rullgard <mans@mansr.com>
> ---
> This patch changes the DT binding, so it should probably be amended for
> compatibility with old device trees.  I've included it as is since I think
> the change as such is good.
> ---
>  Documentation/devicetree/bindings/dma/snps-dma.txt |  5 ++-
>  arch/arc/boot/dts/abilis_tb10x.dtsi                |  2 +-
>  arch/arm/boot/dts/spear13xx.dtsi                   |  4 +--
>  drivers/dma/dw/core.c                              | 40 +++-------------------
>  drivers/dma/dw/platform.c                          |  8 ++---
>  drivers/dma/dw/regs.h                              |  2 +-
>  include/linux/platform_data/dma-dw.h               |  5 ++-
>  7 files changed, 16 insertions(+), 50 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/dma/snps-dma.txt b/Documentation/devicetree/bindings/dma/snps-dma.txt
> index c99c1ffac199..fe7f7710a6b4 100644
> --- a/Documentation/devicetree/bindings/dma/snps-dma.txt
> +++ b/Documentation/devicetree/bindings/dma/snps-dma.txt
> @@ -13,8 +13,7 @@ Required properties:
>  - chan_priority: priority of channels. 0 (default): increase from chan 0->n, 1:
>    increase from chan n->0
>  - block_size: Maximum block size supported by the controller
> -- data_width: Maximum data width supported by hardware per AHB master
> -  (0 - 8bits, 1 - 16bits, ..., 5 - 256bits)
> +- data-width: Maximum data width supported by hardware (in bytes)

To the reader this suggests a value truely byte granular, but code uses ffs
implying that it is still power of 2.
Can you mention this here (....in bytes, always power of 2).

> ...
> @@ -726,10 +710,7 @@ dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
>  
>  	dwc->direction = DMA_MEM_TO_MEM;
>  
> -	data_width = dw->data_width[dwc->m_master];
> -
> -	src_width = dst_width = min_t(unsigned int, data_width,
> -				      dwc_fast_ffs(src | dest | len));
> +	src_width = dst_width = __ffs(dw->data_width | src | dest | len);
> ...

-Vineet
Andy Shevchenko Jan. 25, 2016, 8:42 a.m. UTC | #2
On Sun, 2016-01-24 at 19:21 +0000, Mans Rullgard wrote:
> From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> 
> There are several changes are done here:
> 
>  - Convert the property to be in bytes
> 
>    Much more convenient than keeping encoded value.
> 
>  - Use one value for all AHB masters for now
> 
>    It seems in practice we have no controllers where masters have
> different
>    data bus width, we still might return to distinct values when
> there is a use
>    case.
> 
>  - Rename data_width to data-width in the device tree bindings.
> 
>  - While here, replace dwc_fast_ffs() by __ffs().
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Mans Rullgard <mans@mansr.com>
> ---
> This patch changes the DT binding, so it should probably be amended
> for
> compatibility with old device trees.  I've included it as is since I
> think
> the change as such is good.

So, since all users have at least one master defined, we may easily to
use similar line for old DT variable

if (!of_property_read_u32(np, "data_width", &tmp)) /* removeme: old */
	
pdata->data_width = tmp;
else if (!of_property_read_u32(np, "data-
width", &tmp)) /* removeme: new */
	pdata->data_width = tmp;

I any case Viresh might comment on this since it was his code regarding
to support SPEAr SoCs.

> ---
>  Documentation/devicetree/bindings/dma/snps-dma.txt |  5 ++-
>  arch/arc/boot/dts/abilis_tb10x.dtsi                |  2 +-
>  arch/arm/boot/dts/spear13xx.dtsi                   |  4 +--
>  drivers/dma/dw/core.c                              | 40 +++---------
> ----------
>  drivers/dma/dw/platform.c                          |  8 ++---
>  drivers/dma/dw/regs.h                              |  2 +-
>  include/linux/platform_data/dma-dw.h               |  5 ++-
>  7 files changed, 16 insertions(+), 50 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/dma/snps-dma.txt
> b/Documentation/devicetree/bindings/dma/snps-dma.txt
> index c99c1ffac199..fe7f7710a6b4 100644
> --- a/Documentation/devicetree/bindings/dma/snps-dma.txt
> +++ b/Documentation/devicetree/bindings/dma/snps-dma.txt
> @@ -13,8 +13,7 @@ Required properties:
>  - chan_priority: priority of channels. 0 (default): increase from
> chan 0->n, 1:
>    increase from chan n->0
>  - block_size: Maximum block size supported by the controller
> -- data_width: Maximum data width supported by hardware per AHB
> master
> -  (0 - 8bits, 1 - 16bits, ..., 5 - 256bits)
> +- data-width: Maximum data width supported by hardware (in bytes)
>  
>  
>  Optional properties:
> @@ -38,7 +37,7 @@ Example:
>  		chan_allocation_order = <1>;
>  		chan_priority = <1>;
>  		block_size = <0xfff>;
> -		data_width = <3 3>;
> +		data-width = <8>;
>  	};
>  
>  DMA clients connected to the Designware DMA controller must use the
> format
> diff --git a/arch/arc/boot/dts/abilis_tb10x.dtsi
> b/arch/arc/boot/dts/abilis_tb10x.dtsi
> index cfb5052239a1..2f53bedb0cde 100644
> --- a/arch/arc/boot/dts/abilis_tb10x.dtsi
> +++ b/arch/arc/boot/dts/abilis_tb10x.dtsi
> @@ -112,7 +112,7 @@
>  			chan_allocation_order = <0>;
>  			chan_priority = <1>;
>  			block_size = <0x7ff>;
> -			data_width = <2>;
> +			data-width = <4>;
>  			clocks = <&ahb_clk>;
>  			clock-names = "hclk";
>  		};
> diff --git a/arch/arm/boot/dts/spear13xx.dtsi
> b/arch/arm/boot/dts/spear13xx.dtsi
> index 14594ce8c18a..474b66fa6a32 100644
> --- a/arch/arm/boot/dts/spear13xx.dtsi
> +++ b/arch/arm/boot/dts/spear13xx.dtsi
> @@ -117,7 +117,7 @@
>  			chan_priority = <1>;
>  			block_size = <0xfff>;
>  			dma-masters = <2>;
> -			data_width = <3 3>;
> +			data-width = <8>;
>  		};
>  
>  		dma@eb000000 {
> @@ -133,7 +133,7 @@
>  			chan_allocation_order = <1>;
>  			chan_priority = <1>;
>  			block_size = <0xfff>;
> -			data_width = <3 3>;
> +			data-width = <8>;
>  		};
>  
>  		fsmc: flash@b0000000 {
> diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
> index 140ea59ec882..28278e4c77ad 100644
> --- a/drivers/dma/dw/core.c
> +++ b/drivers/dma/dw/core.c
> @@ -168,21 +168,6 @@ static void dwc_initialize(struct dw_dma_chan
> *dwc)
>  
>  /*----------------------------------------------------------------
> ------*/
>  
> -static inline unsigned int dwc_fast_ffs(unsigned long long v)
> -{
> -	/*
> -	 * We can be a lot more clever here, but this should take
> care
> -	 * of the most common optimization.
> -	 */
> -	if (!(v & 7))
> -		return 3;
> -	else if (!(v & 3))
> -		return 2;
> -	else if (!(v & 1))
> -		return 1;
> -	return 0;
> -}
> -
>  static inline void dwc_dump_chan_regs(struct dw_dma_chan *dwc)
>  {
>  	dev_err(chan2dev(&dwc->chan),
> @@ -712,7 +697,6 @@ dwc_prep_dma_memcpy(struct dma_chan *chan,
> dma_addr_t dest, dma_addr_t src,
>  	size_t			offset;
>  	unsigned int		src_width;
>  	unsigned int		dst_width;
> -	unsigned int		data_width;
>  	u32			ctllo;
>  
>  	dev_vdbg(chan2dev(chan),
> @@ -726,10 +710,7 @@ dwc_prep_dma_memcpy(struct dma_chan *chan,
> dma_addr_t dest, dma_addr_t src,
>  
>  	dwc->direction = DMA_MEM_TO_MEM;
>  
> -	data_width = dw->data_width[dwc->m_master];
> -
> -	src_width = dst_width = min_t(unsigned int, data_width,
> -				      dwc_fast_ffs(src | dest |
> len));
> +	src_width = dst_width = __ffs(dw->data_width | src | dest |
> len);
>  
>  	ctllo = DWC_DEFAULT_CTLLO(chan)
>  			| DWC_CTLL_DST_WIDTH(dst_width)
> @@ -792,7 +773,6 @@ dwc_prep_slave_sg(struct dma_chan *chan, struct
> scatterlist *sgl,
>  	dma_addr_t		reg;
>  	unsigned int		reg_width;
>  	unsigned int		mem_width;
> -	unsigned int		data_width;
>  	unsigned int		i;
>  	struct scatterlist	*sg;
>  	size_t			total_len = 0;
> @@ -818,8 +798,6 @@ dwc_prep_slave_sg(struct dma_chan *chan, struct
> scatterlist *sgl,
>  		ctllo |= sconfig->device_fc ?
> DWC_CTLL_FC(DW_DMA_FC_P_M2P) :
>  			DWC_CTLL_FC(DW_DMA_FC_D_M2P);
>  
> -		data_width = dw->data_width[dwc->m_master];
> -
>  		for_each_sg(sgl, sg, sg_len, i) {
>  			struct dw_desc	*desc;
>  			u32		len, dlen, mem;
> @@ -827,8 +805,7 @@ dwc_prep_slave_sg(struct dma_chan *chan, struct
> scatterlist *sgl,
>  			mem = sg_dma_address(sg);
>  			len = sg_dma_len(sg);
>  
> -			mem_width = min_t(unsigned int,
> -					  data_width,
> dwc_fast_ffs(mem | len));
> +			mem_width = __ffs(dw->data_width | mem |
> len);
>  
>  slave_sg_todev_fill_desc:
>  			desc = dwc_desc_get(dwc);
> @@ -874,8 +851,6 @@ slave_sg_todev_fill_desc:
>  		ctllo |= sconfig->device_fc ?
> DWC_CTLL_FC(DW_DMA_FC_P_P2M) :
>  			DWC_CTLL_FC(DW_DMA_FC_D_P2M);
>  
> -		data_width = dw->data_width[dwc->m_master];
> -
>  		for_each_sg(sgl, sg, sg_len, i) {
>  			struct dw_desc	*desc;
>  			u32		len, dlen, mem;
> @@ -883,8 +858,7 @@ slave_sg_todev_fill_desc:
>  			mem = sg_dma_address(sg);
>  			len = sg_dma_len(sg);
>  
> -			mem_width = min_t(unsigned int,
> -					  data_width,
> dwc_fast_ffs(mem | len));
> +			mem_width = __ffs(dw->data_width | mem |
> len);
>  
>  slave_sg_fromdev_fill_desc:
>  			desc = dwc_desc_get(dwc);
> @@ -1531,10 +1505,7 @@ int dw_dma_probe(struct dw_dma_chip *chip,
> struct dw_dma_platform_data *pdata)
>  		/* Get hardware configuration parameters */
>  		pdata->nr_channels = (dw_params >> DW_PARAMS_NR_CHAN
> & 7) + 1;
>  		pdata->nr_masters = (dw_params >>
> DW_PARAMS_NR_MASTER & 3) + 1;
> -		for (i = 0; i < pdata->nr_masters; i++) {
> -			pdata->data_width[i] =
> -				(dw_params >>
> DW_PARAMS_DATA_WIDTH(i) & 3) + 2;
> -		}
> +		pdata->data_width = 4 << (dw_params >>
> DW_PARAMS_DATA_WIDTH(0) & 3);
>  		max_blk_size = dma_readl(dw, MAX_BLK_SIZE);
>  
>  		/* Fill platform data with the default values */
> @@ -1556,8 +1527,7 @@ int dw_dma_probe(struct dw_dma_chip *chip,
> struct dw_dma_platform_data *pdata)
>  
>  	/* Get hardware configuration parameters */
>  	dw->nr_masters = pdata->nr_masters;
> -	for (i = 0; i < dw->nr_masters; i++)
> -		dw->data_width[i] = pdata->data_width[i];
> +	dw->data_width = pdata->data_width;
>  
>  	/* Calculate all channel mask before DMA setup */
>  	dw->all_chan_mask = (1 << pdata->nr_channels) - 1;
> diff --git a/drivers/dma/dw/platform.c b/drivers/dma/dw/platform.c
> index d3e1abcebd7f..89d0461f5dcc 100644
> --- a/drivers/dma/dw/platform.c
> +++ b/drivers/dma/dw/platform.c
> @@ -102,8 +102,8 @@ dw_dma_parse_dt(struct platform_device *pdev)
>  {
>  	struct device_node *np = pdev->dev.of_node;
>  	struct dw_dma_platform_data *pdata;
> -	u32 tmp, arr[DW_DMA_MAX_NR_MASTERS];
>  	u32 nr_channels;
> +	u32 tmp;
>  
>  	if (!np) {
>  		dev_err(&pdev->dev, "Missing DT data\n");
> @@ -138,10 +138,8 @@ dw_dma_parse_dt(struct platform_device *pdev)
>  		pdata->nr_masters = tmp;
>  	}
>  
> -	if (!of_property_read_u32_array(np, "data_width", arr,
> -				pdata->nr_masters))
> -		for (tmp = 0; tmp < pdata->nr_masters; tmp++)
> -			pdata->data_width[tmp] = arr[tmp];
> +	if (!of_property_read_u32(np, "data-width", &tmp))
> +		pdata->data_width = tmp;
>  
>  	return pdata;
>  }
> diff --git a/drivers/dma/dw/regs.h b/drivers/dma/dw/regs.h
> index e4b277565165..87bc97fca084 100644
> --- a/drivers/dma/dw/regs.h
> +++ b/drivers/dma/dw/regs.h
> @@ -285,7 +285,7 @@ struct dw_dma {
>  
>  	/* hardware configuration */
>  	unsigned char		nr_masters;
> -	unsigned char		data_width[DW_DMA_MAX_NR_MASTER
> S];
> +	unsigned char		data_width;
>  };
>  
>  static inline struct dw_dma_regs __iomem *__dw_regs(struct dw_dma
> *dw)
> diff --git a/include/linux/platform_data/dma-dw.h
> b/include/linux/platform_data/dma-dw.h
> index b881b978e486..4120a3eb71ca 100644
> --- a/include/linux/platform_data/dma-dw.h
> +++ b/include/linux/platform_data/dma-dw.h
> @@ -42,8 +42,7 @@ struct dw_dma_slave {
>   * @chan_priority: Set channel priority increasing from 0 to 7 or 7
> to 0.
>   * @block_size: Maximum block size supported by the controller
>   * @nr_masters: Number of AHB masters supported by the controller
> - * @data_width: Maximum data width supported by hardware per AHB
> master
> - *		(0 - 8bits, 1 - 16bits, ..., 5 - 256bits)
> + * @data_width: Maximum data width supported by hardware (in bytes)
>   */
>  struct dw_dma_platform_data {
>  	unsigned int	nr_channels;
> @@ -57,7 +56,7 @@ struct dw_dma_platform_data {
>  	unsigned char	chan_priority;
>  	unsigned short	block_size;
>  	unsigned char	nr_masters;
> -	unsigned char	data_width[DW_DMA_MAX_NR_MASTERS];
> +	unsigned char	data_width;
>  };
>  
>  #endif /* _PLATFORM_DATA_DMA_DW_H */
Andy Shevchenko Jan. 25, 2016, 8:45 a.m. UTC | #3
On Mon, 2016-01-25 at 07:32 +0000, Vineet Gupta wrote:
> On Monday 25 January 2016 12:55 AM, Mans Rullgard wrote:
> > From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > 
> > There are several changes are done here:
> > 
> >  - Convert the property to be in bytes
> > 
> >    Much more convenient than keeping encoded value.
> > 
> >  - Use one value for all AHB masters for now
> > 
> >    It seems in practice we have no controllers where masters have
> > different
> >    data bus width, we still might return to distinct values when
> > there is a use
> >    case.
> > 
> >  - Rename data_width to data-width in the device tree bindings.
> > 
> >  - While here, replace dwc_fast_ffs() by __ffs().
> > 
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > Signed-off-by: Mans Rullgard <mans@mansr.com>
> > ---
> > This patch changes the DT binding, so it should probably be amended
> > for
> > compatibility with old device trees.  I've included it as is since
> > I think
> > the change as such is good.
> > ---
> >  Documentation/devicetree/bindings/dma/snps-dma.txt |  5 ++-
> >  arch/arc/boot/dts/abilis_tb10x.dtsi                |  2 +-
> >  arch/arm/boot/dts/spear13xx.dtsi                   |  4 +--
> >  drivers/dma/dw/core.c                              | 40 +++-------
> > ------------
> >  drivers/dma/dw/platform.c                          |  8 ++---
> >  drivers/dma/dw/regs.h                              |  2 +-
> >  include/linux/platform_data/dma-dw.h               |  5 ++-
> >  7 files changed, 16 insertions(+), 50 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/dma/snps-dma.txt
> > b/Documentation/devicetree/bindings/dma/snps-dma.txt
> > index c99c1ffac199..fe7f7710a6b4 100644
> > --- a/Documentation/devicetree/bindings/dma/snps-dma.txt
> > +++ b/Documentation/devicetree/bindings/dma/snps-dma.txt
> > @@ -13,8 +13,7 @@ Required properties:
> >  - chan_priority: priority of channels. 0 (default): increase from
> > chan 0->n, 1:
> >    increase from chan n->0
> >  - block_size: Maximum block size supported by the controller
> > -- data_width: Maximum data width supported by hardware per AHB
> > master
> > -  (0 - 8bits, 1 - 16bits, ..., 5 - 256bits)
> > +- data-width: Maximum data width supported by hardware (in bytes)
> 
> To the reader this suggests a value truely byte granular, but code
> uses ffs
> implying that it is still power of 2.
> Can you mention this here (....in bytes, always power of 2).

While this comment is good, I have still note that using non-power of 2
values will not break anything. Least power of two number will be used
in that case. So, means I would suggest to replace 'always' by 'better
to be' or something like that.

> 
> > ...
> > @@ -726,10 +710,7 @@ dwc_prep_dma_memcpy(struct dma_chan *chan,
> > dma_addr_t dest, dma_addr_t src,
> >  
> >  	dwc->direction = DMA_MEM_TO_MEM;
> >  
> > -	data_width = dw->data_width[dwc->m_master];
> > -
> > -	src_width = dst_width = min_t(unsigned int, data_width,
> > -				      dwc_fast_ffs(src | dest |
> > len));
> > +	src_width = dst_width = __ffs(dw->data_width | src | dest
> > | len);
> > ...
> 
> -Vineet
Mans Rullgard Jan. 25, 2016, 10:31 a.m. UTC | #4
Andy Shevchenko <andriy.shevchenko@linux.intel.com> writes:

> On Mon, 2016-01-25 at 07:32 +0000, Vineet Gupta wrote:
>> On Monday 25 January 2016 12:55 AM, Mans Rullgard wrote:
>> > From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>> > 
>> > There are several changes are done here:
>> > 
>> >  - Convert the property to be in bytes
>> > 
>> >    Much more convenient than keeping encoded value.
>> > 
>> >  - Use one value for all AHB masters for now
>> > 
>> >    It seems in practice we have no controllers where masters have
>> > different
>> >    data bus width, we still might return to distinct values when
>> > there is a use
>> >    case.
>> > 
>> >  - Rename data_width to data-width in the device tree bindings.
>> > 
>> >  - While here, replace dwc_fast_ffs() by __ffs().
>> > 
>> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>> > Signed-off-by: Mans Rullgard <mans@mansr.com>
>> > ---
>> > This patch changes the DT binding, so it should probably be amended
>> > for
>> > compatibility with old device trees.  I've included it as is since
>> > I think
>> > the change as such is good.
>> > ---
>> >  Documentation/devicetree/bindings/dma/snps-dma.txt |  5 ++-
>> >  arch/arc/boot/dts/abilis_tb10x.dtsi                |  2 +-
>> >  arch/arm/boot/dts/spear13xx.dtsi                   |  4 +--
>> >  drivers/dma/dw/core.c                              | 40 +++-------
>> > ------------
>> >  drivers/dma/dw/platform.c                          |  8 ++---
>> >  drivers/dma/dw/regs.h                              |  2 +-
>> >  include/linux/platform_data/dma-dw.h               |  5 ++-
>> >  7 files changed, 16 insertions(+), 50 deletions(-)
>> > 
>> > diff --git a/Documentation/devicetree/bindings/dma/snps-dma.txt
>> > b/Documentation/devicetree/bindings/dma/snps-dma.txt
>> > index c99c1ffac199..fe7f7710a6b4 100644
>> > --- a/Documentation/devicetree/bindings/dma/snps-dma.txt
>> > +++ b/Documentation/devicetree/bindings/dma/snps-dma.txt
>> > @@ -13,8 +13,7 @@ Required properties:
>> >  - chan_priority: priority of channels. 0 (default): increase from
>> > chan 0->n, 1:
>> >    increase from chan n->0
>> >  - block_size: Maximum block size supported by the controller
>> > -- data_width: Maximum data width supported by hardware per AHB
>> > master
>> > -  (0 - 8bits, 1 - 16bits, ..., 5 - 256bits)
>> > +- data-width: Maximum data width supported by hardware (in bytes)
>> 
>> To the reader this suggests a value truely byte granular, but code
>> uses ffs
>> implying that it is still power of 2.
>> Can you mention this here (....in bytes, always power of 2).
>
> While this comment is good, I have still note that using non-power of 2
> values will not break anything. Least power of two number will be used
> in that case. So, means I would suggest to replace 'always' by 'better
> to be' or something like that.

Although the code rounds down, the hardware actually works in powers of
two, and it's better to document this.
Andy Shevchenko Jan. 25, 2016, 10:36 a.m. UTC | #5
On Mon, 2016-01-25 at 10:31 +0000, Måns Rullgård wrote:
> Andy Shevchenko <andriy.shevchenko@linux.intel.com> writes:
> 
> > On Mon, 2016-01-25 at 07:32 +0000, Vineet Gupta wrote:
> > > On Monday 25 January 2016 12:55 AM, Mans Rullgard wrote:

> > > > --- a/Documentation/devicetree/bindings/dma/snps-dma.txt
> > > > +++ b/Documentation/devicetree/bindings/dma/snps-dma.txt
> > > > @@ -13,8 +13,7 @@ Required properties:
> > > >  - chan_priority: priority of channels. 0 (default): increase
> > > > from
> > > > chan 0->n, 1:
> > > >    increase from chan n->0
> > > >  - block_size: Maximum block size supported by the controller
> > > > -- data_width: Maximum data width supported by hardware per AHB
> > > > master
> > > > -  (0 - 8bits, 1 - 16bits, ..., 5 - 256bits)
> > > > +- data-width: Maximum data width supported by hardware (in
> > > > bytes)
> > > 
> > > To the reader this suggests a value truely byte granular, but
> > > code
> > > uses ffs
> > > implying that it is still power of 2.
> > > Can you mention this here (....in bytes, always power of 2).
> > 
> > While this comment is good, I have still note that using non-power
> > of 2
> > values will not break anything. Least power of two number will be
> > used
> > in that case. So, means I would suggest to replace 'always' by
> > 'better
> > to be' or something like that.
> 
> Although the code rounds down, the hardware actually works in powers
> of
> two, and it's better to document this.

Let's do "(in bytes, power of 2)" then?
Rob Herring Jan. 26, 2016, 9:07 p.m. UTC | #6
On Sun, Jan 24, 2016 at 07:21:54PM +0000, Mans Rullgard wrote:
> From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> 
> There are several changes are done here:
> 
>  - Convert the property to be in bytes
> 
>    Much more convenient than keeping encoded value.
> 
>  - Use one value for all AHB masters for now
> 
>    It seems in practice we have no controllers where masters have different
>    data bus width, we still might return to distinct values when there is a use
>    case.
> 
>  - Rename data_width to data-width in the device tree bindings.
> 
>  - While here, replace dwc_fast_ffs() by __ffs().
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Mans Rullgard <mans@mansr.com>
> ---
> This patch changes the DT binding, so it should probably be amended for
> compatibility with old device trees.  I've included it as is since I think
> the change as such is good.

Just because you update the dts files, it doesn't make the change okay. 
I'm fine with the DT change, but the driver would have to support both 
old and new property names. Doesn't really seem worth doing to me.

Rob
Andy Shevchenko Jan. 27, 2016, 12:26 p.m. UTC | #7
On Tue, 2016-01-26 at 15:07 -0600, Rob Herring wrote:
> On Sun, Jan 24, 2016 at 07:21:54PM +0000, Mans Rullgard wrote:

> > This patch changes the DT binding, so it should probably be amended
> > for
> > compatibility with old device trees.  I've included it as is since
> > I think
> > the change as such is good.
> 
> Just because you update the dts files, it doesn't make the change
> okay. 
> I'm fine with the DT change, but the driver would have to support
> both 
> old and new property names.

We will fix this.

>  Doesn't really seem worth doing to me.

The big issue with DT, you know, is hanging around names. This moves
name to be de facto standard for similar in the other drivers.

Patch
diff mbox

diff --git a/Documentation/devicetree/bindings/dma/snps-dma.txt b/Documentation/devicetree/bindings/dma/snps-dma.txt
index c99c1ffac199..fe7f7710a6b4 100644
--- a/Documentation/devicetree/bindings/dma/snps-dma.txt
+++ b/Documentation/devicetree/bindings/dma/snps-dma.txt
@@ -13,8 +13,7 @@  Required properties:
 - chan_priority: priority of channels. 0 (default): increase from chan 0->n, 1:
   increase from chan n->0
 - block_size: Maximum block size supported by the controller
-- data_width: Maximum data width supported by hardware per AHB master
-  (0 - 8bits, 1 - 16bits, ..., 5 - 256bits)
+- data-width: Maximum data width supported by hardware (in bytes)
 
 
 Optional properties:
@@ -38,7 +37,7 @@  Example:
 		chan_allocation_order = <1>;
 		chan_priority = <1>;
 		block_size = <0xfff>;
-		data_width = <3 3>;
+		data-width = <8>;
 	};
 
 DMA clients connected to the Designware DMA controller must use the format
diff --git a/arch/arc/boot/dts/abilis_tb10x.dtsi b/arch/arc/boot/dts/abilis_tb10x.dtsi
index cfb5052239a1..2f53bedb0cde 100644
--- a/arch/arc/boot/dts/abilis_tb10x.dtsi
+++ b/arch/arc/boot/dts/abilis_tb10x.dtsi
@@ -112,7 +112,7 @@ 
 			chan_allocation_order = <0>;
 			chan_priority = <1>;
 			block_size = <0x7ff>;
-			data_width = <2>;
+			data-width = <4>;
 			clocks = <&ahb_clk>;
 			clock-names = "hclk";
 		};
diff --git a/arch/arm/boot/dts/spear13xx.dtsi b/arch/arm/boot/dts/spear13xx.dtsi
index 14594ce8c18a..474b66fa6a32 100644
--- a/arch/arm/boot/dts/spear13xx.dtsi
+++ b/arch/arm/boot/dts/spear13xx.dtsi
@@ -117,7 +117,7 @@ 
 			chan_priority = <1>;
 			block_size = <0xfff>;
 			dma-masters = <2>;
-			data_width = <3 3>;
+			data-width = <8>;
 		};
 
 		dma@eb000000 {
@@ -133,7 +133,7 @@ 
 			chan_allocation_order = <1>;
 			chan_priority = <1>;
 			block_size = <0xfff>;
-			data_width = <3 3>;
+			data-width = <8>;
 		};
 
 		fsmc: flash@b0000000 {
diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index 140ea59ec882..28278e4c77ad 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -168,21 +168,6 @@  static void dwc_initialize(struct dw_dma_chan *dwc)
 
 /*----------------------------------------------------------------------*/
 
-static inline unsigned int dwc_fast_ffs(unsigned long long v)
-{
-	/*
-	 * We can be a lot more clever here, but this should take care
-	 * of the most common optimization.
-	 */
-	if (!(v & 7))
-		return 3;
-	else if (!(v & 3))
-		return 2;
-	else if (!(v & 1))
-		return 1;
-	return 0;
-}
-
 static inline void dwc_dump_chan_regs(struct dw_dma_chan *dwc)
 {
 	dev_err(chan2dev(&dwc->chan),
@@ -712,7 +697,6 @@  dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 	size_t			offset;
 	unsigned int		src_width;
 	unsigned int		dst_width;
-	unsigned int		data_width;
 	u32			ctllo;
 
 	dev_vdbg(chan2dev(chan),
@@ -726,10 +710,7 @@  dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 
 	dwc->direction = DMA_MEM_TO_MEM;
 
-	data_width = dw->data_width[dwc->m_master];
-
-	src_width = dst_width = min_t(unsigned int, data_width,
-				      dwc_fast_ffs(src | dest | len));
+	src_width = dst_width = __ffs(dw->data_width | src | dest | len);
 
 	ctllo = DWC_DEFAULT_CTLLO(chan)
 			| DWC_CTLL_DST_WIDTH(dst_width)
@@ -792,7 +773,6 @@  dwc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 	dma_addr_t		reg;
 	unsigned int		reg_width;
 	unsigned int		mem_width;
-	unsigned int		data_width;
 	unsigned int		i;
 	struct scatterlist	*sg;
 	size_t			total_len = 0;
@@ -818,8 +798,6 @@  dwc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 		ctllo |= sconfig->device_fc ? DWC_CTLL_FC(DW_DMA_FC_P_M2P) :
 			DWC_CTLL_FC(DW_DMA_FC_D_M2P);
 
-		data_width = dw->data_width[dwc->m_master];
-
 		for_each_sg(sgl, sg, sg_len, i) {
 			struct dw_desc	*desc;
 			u32		len, dlen, mem;
@@ -827,8 +805,7 @@  dwc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 			mem = sg_dma_address(sg);
 			len = sg_dma_len(sg);
 
-			mem_width = min_t(unsigned int,
-					  data_width, dwc_fast_ffs(mem | len));
+			mem_width = __ffs(dw->data_width | mem | len);
 
 slave_sg_todev_fill_desc:
 			desc = dwc_desc_get(dwc);
@@ -874,8 +851,6 @@  slave_sg_todev_fill_desc:
 		ctllo |= sconfig->device_fc ? DWC_CTLL_FC(DW_DMA_FC_P_P2M) :
 			DWC_CTLL_FC(DW_DMA_FC_D_P2M);
 
-		data_width = dw->data_width[dwc->m_master];
-
 		for_each_sg(sgl, sg, sg_len, i) {
 			struct dw_desc	*desc;
 			u32		len, dlen, mem;
@@ -883,8 +858,7 @@  slave_sg_todev_fill_desc:
 			mem = sg_dma_address(sg);
 			len = sg_dma_len(sg);
 
-			mem_width = min_t(unsigned int,
-					  data_width, dwc_fast_ffs(mem | len));
+			mem_width = __ffs(dw->data_width | mem | len);
 
 slave_sg_fromdev_fill_desc:
 			desc = dwc_desc_get(dwc);
@@ -1531,10 +1505,7 @@  int dw_dma_probe(struct dw_dma_chip *chip, struct dw_dma_platform_data *pdata)
 		/* Get hardware configuration parameters */
 		pdata->nr_channels = (dw_params >> DW_PARAMS_NR_CHAN & 7) + 1;
 		pdata->nr_masters = (dw_params >> DW_PARAMS_NR_MASTER & 3) + 1;
-		for (i = 0; i < pdata->nr_masters; i++) {
-			pdata->data_width[i] =
-				(dw_params >> DW_PARAMS_DATA_WIDTH(i) & 3) + 2;
-		}
+		pdata->data_width = 4 << (dw_params >> DW_PARAMS_DATA_WIDTH(0) & 3);
 		max_blk_size = dma_readl(dw, MAX_BLK_SIZE);
 
 		/* Fill platform data with the default values */
@@ -1556,8 +1527,7 @@  int dw_dma_probe(struct dw_dma_chip *chip, struct dw_dma_platform_data *pdata)
 
 	/* Get hardware configuration parameters */
 	dw->nr_masters = pdata->nr_masters;
-	for (i = 0; i < dw->nr_masters; i++)
-		dw->data_width[i] = pdata->data_width[i];
+	dw->data_width = pdata->data_width;
 
 	/* Calculate all channel mask before DMA setup */
 	dw->all_chan_mask = (1 << pdata->nr_channels) - 1;
diff --git a/drivers/dma/dw/platform.c b/drivers/dma/dw/platform.c
index d3e1abcebd7f..89d0461f5dcc 100644
--- a/drivers/dma/dw/platform.c
+++ b/drivers/dma/dw/platform.c
@@ -102,8 +102,8 @@  dw_dma_parse_dt(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
 	struct dw_dma_platform_data *pdata;
-	u32 tmp, arr[DW_DMA_MAX_NR_MASTERS];
 	u32 nr_channels;
+	u32 tmp;
 
 	if (!np) {
 		dev_err(&pdev->dev, "Missing DT data\n");
@@ -138,10 +138,8 @@  dw_dma_parse_dt(struct platform_device *pdev)
 		pdata->nr_masters = tmp;
 	}
 
-	if (!of_property_read_u32_array(np, "data_width", arr,
-				pdata->nr_masters))
-		for (tmp = 0; tmp < pdata->nr_masters; tmp++)
-			pdata->data_width[tmp] = arr[tmp];
+	if (!of_property_read_u32(np, "data-width", &tmp))
+		pdata->data_width = tmp;
 
 	return pdata;
 }
diff --git a/drivers/dma/dw/regs.h b/drivers/dma/dw/regs.h
index e4b277565165..87bc97fca084 100644
--- a/drivers/dma/dw/regs.h
+++ b/drivers/dma/dw/regs.h
@@ -285,7 +285,7 @@  struct dw_dma {
 
 	/* hardware configuration */
 	unsigned char		nr_masters;
-	unsigned char		data_width[DW_DMA_MAX_NR_MASTERS];
+	unsigned char		data_width;
 };
 
 static inline struct dw_dma_regs __iomem *__dw_regs(struct dw_dma *dw)
diff --git a/include/linux/platform_data/dma-dw.h b/include/linux/platform_data/dma-dw.h
index b881b978e486..4120a3eb71ca 100644
--- a/include/linux/platform_data/dma-dw.h
+++ b/include/linux/platform_data/dma-dw.h
@@ -42,8 +42,7 @@  struct dw_dma_slave {
  * @chan_priority: Set channel priority increasing from 0 to 7 or 7 to 0.
  * @block_size: Maximum block size supported by the controller
  * @nr_masters: Number of AHB masters supported by the controller
- * @data_width: Maximum data width supported by hardware per AHB master
- *		(0 - 8bits, 1 - 16bits, ..., 5 - 256bits)
+ * @data_width: Maximum data width supported by hardware (in bytes)
  */
 struct dw_dma_platform_data {
 	unsigned int	nr_channels;
@@ -57,7 +56,7 @@  struct dw_dma_platform_data {
 	unsigned char	chan_priority;
 	unsigned short	block_size;
 	unsigned char	nr_masters;
-	unsigned char	data_width[DW_DMA_MAX_NR_MASTERS];
+	unsigned char	data_width;
 };
 
 #endif /* _PLATFORM_DATA_DMA_DW_H */